Onto version 2.0
changes from the initial prototype:
-implement wayne's excellent suggestions from post #11
his lcr pan scheme
-digital switching of pan,phantom, phase, gain control
-replace bluetooth/android interface with mini oled/5-way mini joystick
-reduce power rails to ~ +/6v
-mcu and summing section integrated onto backplane
-AT328p MCU @8Mhz 3.3v (shrinkified arduino pro mini = mcu+4 passives)
-have p/s and preamp cards properly removable with edge connector
-maybe 5v and or usb powered main supply since rails will be lower now
-fit it properly in tin this time, last go round it was slightly too large
-reduce to 5 channels in order to fit in screen/mini joystick/mcu controller on the backplane
-maybe some led level metering
I have the physical layout near where I want it. Without finding these samtec mini edge connectors I would not have been able to make these cards modular. Working with mini pitch headers was a nightmare on the last version.
There is some regret in lowering the channel count but there's no way to fit 6 channels in with these edge connectors and the mini oled screen. Also a little regret in ditching the android bluetooth interface, especially because it worked. But I'm leaning toward having everything in one box.
I checked the visibility/workability of this .66" screen and it's just about perfect. The contrast is high enough that it offsets the small characters. I'm planning on two screens: main screen for gain and pan --->>navigated to a secondary screen for phantom and phase. I can't fit everything into one screen of 64x48 characters.
The mcu runs at 3.3v, the oled runs as 3.3v, and THAT spi runs 3.3v. The screen actually wants 7v but it has an onboard charge pump that takes 3.3v and I suppose doubles it and 6.6v is close enough.
Will post schems soon. Have never done any digi controlled switches so I need to read up, and haven't figured out how or if to tie in all the device resets.